Single crystals are typically brittle, inelastic materials. Such mechanical responses limit their use in practical applications, particularly in flexible electronics and optical devices. Here we describe single crystals of a well-known coordination compound—copper(II) acetylacetonate—that are flexible enough to be reversibly tied into a knot. Mechanical measurements indicate that the crystals exhibit an elasticity similar to that of soft materials such as nylon, and thus display properties normally associated with both hard and soft matter. Using microfocused synchrotron radiation, we mapped the changes in crystal structure that occur on bending, and determined the mechanism that allows this flexibility with atomic precision. We show that, under strain, the molecules in the crystal reversibly rotate, and thus reorganize to allow the mechanical compression and expansion required for elasticity and still maintain the integrity of the crystal structure.
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Dove, M. T. Structure and Dynamics: An Atomic View of Materials (Oxford Univ. Press, 2003).
Chen, W., Qi, D.-C., Huang, H., Gao, X. & Wee, A. T. S. Organic–organic heterojunction interfaces: effect of molecular orientation. Adv. Funct. Mater. 21, 410–424 (2011).
Shaw, P. E., Wolfer, P., Langley, B., Burn, P. L. & Meredith, P. Impact of acceptor crystallinity on the photophysics of nonfullerene blends for organic solar cells. J. Phys. Chem. C 118, 13460–13466 (2014).
Huang, M. H. et al. Room-temperature ultraviolet nanowire nanolasers. Science 292, 1897–1899 (2001).
Krause, S. et al. A pressure-amplifying framework material with negative gas adsorption transitions. Nature 532, 348–352 (2016).
Schmidt-Mende, L. et al. Self-organized discotic liquid crystals for high-efficiency organic photovoltaics. Science 293, 1119–1122 (2001).
Bronstein, H. et al. Thieno[3,2-b]thiophene−diketopyrrolopyrrole-containing polymers for high-performance organic field-effect transistors and organic photovoltaic devices. J. Am. Chem. Soc. 133, 3272–3275 (2011).
Somiya, S. Handbook of Advanced Ceramics: Materials, Applications, Processing, and Properties 2nd edn (Academic, 2013).
Reddy, C. M., Rama Krishna, G. & Ghosh, S. Mechanical properties of molecular crystals-applications to crystal engineering. CrystEngComm 12, 2296–2314 (2010).
Reddy, C. M., Padmanabhan, K. A. & Desiraju, G. R. Structure–property correlations in bending and brittle organic crystals. Cryst. Growth Des. 6, 2720–2731 (2006).
Panda, M. K. et al. Spatially resolved analysis of short-range structure perturbations in a plastically bent molecular crystal. Nat. Chem. 7, 65–72 (2015).
Reddy, C. M. et al. Structural basis for bending of organic crystals. Chem. Commun. 3945–3947 (2005).
Duyker, S. G., Peterson, V. K., Kearley, G. J., Studer, A. J. & Kepert, C. J. Extreme compressibility in LnFe(CN)6 coordination framework materials via molecular gears and torsion springs. Nat. Chem. 8, 270–275 (2016).
Goodwin, A. L. et al. Colossal positive and negative thermal expansion in the framework material Ag3[Co(CN)6]. Science 319, 794–797 (2008).
Commins, P., Desta, I. T., Karothu, D. P., Panda, M. K. & Naumov, P. Crystals on the move: mechanical effects in dynamic solids. Chem. Commun. 52, 13941–13954 (2016).
Takamizawa, S. & Miyamoto, Y. Superelastic organic crystals. Angew. Chem. Int. Ed. 53, 6970–6973 (2014).
Werner, A. Über Acetylacetonverbindungen des Platins. Ber. Deut. Chem. Ges. 34, 2584–2593 (1901).
Starikova, Z. A. & Shugam, E. A. Crystal chemical data for inner complexes of β-diketones. J. Struct. Chem. 10, 267–269 (1969).
Lebrun, P. C., Lyon, W. D. & Kuska, H. A. Crystal structure of bis(2,4-pentanedionato)copper(II). J. Crystallogr. Spectrosc. Res. 16, 889–893 (1986).
Vreshch, V. D., Yang, J.-H., Zhang, H., Filatov, A. S. & Dikarev, E. V. Monomeric square-planar cobalt(II) acetylacetonate: mystery or mistake? Inorg. Chem. 49, 8430–8434 (2010).
Golchoubian, H. Redetermination of crystal structure of bis(2,4-pentanedionato)copper(II). Asian J. Chem. 20, 5834–5838 (2008).
Hamid, M., Mazhar, M., Zeller, M. & Hunter, A. D. CCDC 281026. CSD Communication doi: 10.5517/cc9ffch (2005).
Berry, G., Callon, G., Gowans, B., Low, J. N. & Smith, R. CCDC 228882. CSD Communication doi: 10.5517/cc7p59c (2004).
Janiak, C. A critical account of π–π stacking in metal complexes with aromatic nitrogen containing ligands. J. Chem. Soc. Dalton Trans. 3885–3896 (2000).
Hunter, C. A. & Sanders, J. K. M. The nature of π–π interactions. J. Am. Chem. Soc. 112, 5525–5534 (1990).
Heine, K. B. et al. Complexation, computational, magnetic, and structural studies of the Maillard reaction product isomaltol including investigation of an uncommon π interaction with copper(II). Inorg. Chem. 50, 1498–1505 (2011).
Tan, J. C. & Cheetham, A. K. Mechanical properties of hybrid inorganic–organic framework materials: establishing fundamental structure–property relationships. Chem. Soc. Rev. 40, 1059–1080 (2010).
Keen, D. A. & Goodwin, A. L. The crystallography of correlated disorder. Nature 521, 303–309 (2015).
Ghosh, S. & Reddy, C. M. Elastic and bendable caffeine cocrystals: implications for the design of flexible organic materials. Angew. Chem. Int. Ed. 51, 10319–10323 (2012).
Ghosh, S., Mishra, M. K., Ganguly, S. & Desiraju, G. R. Dual stress and thermally driven mechanical properties of the same organic crystal: 2,6-dichlorobenzylidene-4-fluoro-3-nitroaniline. J. Am. Chem. Soc. 137, 9912–9921 (2015).
Ghosh, S., Mishra, M. K., Kadambi, S. B., Ramamurty, U. & Desiraju, G. R. Designing elastic organic crystals: highly flexible polyhalogenated N-benzylideneanilines. Angew. Chem. Int. Ed. 54, 2674–2678 (2015).
Holtzclaw, H. F., Johnson, K. W. R. & Hengeveld, F. W. Polarographic reduction of the copper derivatives of several 1,3-diketones in various solvents. J. Am. Chem. Soc. 74, 3776–3778 (1952).
TI 950 TriboIndenter User Manual Revision 9.2.1211 (Hysitron Inc., 2011).
McPhillips, T. M. et al. Blu-Ice and the distributed control system: software for data acquisition and instrument control at macromolecular crystallography beamlines. J. Synchrotron Rad. 9, 401–406 (2002).
Kabsch, W. Automatic processing of rotation diffraction data from crystals of initially unknown symmetry and cell constants. J. Appl. Cryst. 26, 795–800 (1993).
Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. OLEX2: a complete structure solution, refinement and analysis program. J. Appl. Cryst. 42, 339–341 (2009).
Sheldrick, G. M. SHELXT—integrated space-group and crystal-structure determination. Acta Cryst. A71, 3–8 (2015).
Sheldrick, G. M. Crystal structure refinement with SHELXL. Acta Cryst. C71, 3–8 (2015).
We thank the Australian Research Council for support. Part of this research was undertaken on the MX1 and MX2 beamlines of the Australian Synchrotron, Clayton, Victoria, Australia. We thank Australian Synchrotron for travel support and their staff for assistance. We thank the University of Queensland, Queensland University of Technology and the Central Analytical Research Facility (CARF, QUT) for support.
The authors declare no competing financial interests.
Supplementary information (PDF 4957 kb)
Supplementary Movie 1 (MP4 35949 kb)
Supplementary Movie 2 (MP4 6669 kb)
Crystallographic data for the unbent [Cu(acac)2] (CIF 299 kb)
Crystallographic data for Crystal 1 (structures a to p) (CIF 355 kb)
Crystallographic data for Crystal 2 (structures a to r) (CIF 420 kb)
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Worthy, A., Grosjean, A., Pfrunder, M. et al. Atomic resolution of structural changes in elastic crystals of copper(II) acetylacetonate. Nature Chem 10, 65–69 (2018). https://doi.org/10.1038/nchem.2848
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